DE 10 2005 035 452 A1 discloses a lubricant dispenser having a housing whose interior is subdivided by a shiftable piston into a generally closed gas compartment and a lubricant compartment having an outlet port and filled with a body of lubricant. A gas generator associated with the gas compartment is electrically energizable to produce gas and thereby pressurize the gas compartment, shift the piston, and express lubricant from the outlet. A controller including a power supply and a circuit is connected between the power supply and the gas generator for feeding current from the power supply to the gas generator. Normally the generator is constructed such that the rate (volume/time) of gas it generates is related to the current level applied to it. Such a gas generator can be a current-generating zinc-air cell or the power supply can be a lithium battery.
The gas-generation rate may be controlled by means of the controller so that a discontinuous supply of lubricant is possible. With regard to the amount of lubricant supplied, it is assumed that the amount of gas emitted by the gas generator is proportional to the amount of lubricant emitted. In practice, however, considerable deviations from proportionality of this sort have been observed, in particular at the start of an operational cycle and again after it has been running for a while.
DE 37 22 708 discloses a lubricant dispenser that has a container with an electrolyte liquid as its gas generating element. In order to generate the gas, voltage provided by a battery is applied to the electrolyte liquid via electrodes. Here as well, the gas-generation rate is presumed to be proportional to the rate of current. Because the electrolysis process is temperature dependent to a large degree, a change in the gas-generation rate is observed at a predetermined differential voltage on the electrodes at different temperatures. For this reason, a controller is provided that does not keep the voltage on the electrodes constant, but rather the current level. On startup, in spite of the constant current, lubricant is nonetheless emitted only after a certain delay, and a certain reduction in the amount of lubricant emitted may also occur as the lubrication process proceeds.
U.S. Pat. No. 5,968,325 discloses a gas-generation element for a lubricant dispenser embodied as a galvanic cell that is distinguished by a low degree of temperature dependence. In order to guarantee uniform emission of lubricant, the controller may be provided with a temperature and/or pressure sensor as part of a feedback-control system. Providing and mounting the sensor in the housing increases production costs for the lubricant dispenser, and a correspondingly expensive controller is necessary as well in order to process the sensor data.